Most conventional direct reduction (DR) plants in the world were designed and are operated to produce, cool, and discharge direct reduced iron (DRI) at temperatures of less than about 100 degrees C. These DR plants are typically located in or adjacent to a steelmaking complex and the DRI is used in a nearby electric arc furnace (EAF). Some DR plants, however, are not located in or adjacent to a steelmaking complex. These are primarily merchant DR plants, selling DRI in the worldwide market. The merchant DR plants prefer to sell DRI that has been compacted and densified, making handling, storage, and shipping easier and safer. The merchant DR plants typically briquette DRI while it is still hot (i.e. greater than about 600 degrees C.) in order to get a high apparent density of hot briquetted iron (HBI). HBI is typically made by reducing pellets and lumps in a DR shaft furnace or iron fines in a fluidized bed reactor and feeding the hot direct reduced iron (HDRI) directly and continuously to the hot briquetting plant. After briquetting, the HBI is cooled to less than about 100 degrees C. for shipping.
In addition to these conventional DR and HBI plants, there are plants that are either utilizing or would like to utilize HDRI from the DR plant in the adjacent steelmaking complex, instead of feeding cold DRI to the melting furnace. In addition to feeding HDRI to the melting furnace, these plants would like to hot briquette any excess HDRI from the DR plant. This HBI may be stockpiled and utilized at a later date in the steelmaking complex, or may be sold as HBI to third parties.
Two early Purofer DR plants (currently inoperable) produced HBI by discharging HDRI from a DR shaft furnace into containers, and then moved the containers to a hot briquetting plant for HBI production. One of these Purofer DR plants also used the containers to charge the HDRI to a steelmaking furnace. Likewise, a plant in India is currently producing and feeding HDRI from a DR shaft furnace to both a hot briquetting plant and insulated containers that are transported to an adjacent melting furnace for steel production.
The concept of producing HDRI in a solid coal-based DR plant and discharging it to a variety of downstream uses or systems, such as a hot briquetting plant, insulated containers, a melter, or a cooler is well known to those of ordinary skill in the art. For example, U.S. Pat. No. 5,873,925, Rinker et al., discloses the discharge of HDRI from a coal-based rotary hearth furnace to an insulated container, a hot compaction unit, or a cooler. U.S. Pat. No. 5,570,775, Meissner et al., discloses the discharge of HDRI from a coal-based rotary hearth furnace to a hot briquetting plant or hot transfer bin, insulated containers, a melter, or a cooler. GB 1,004,428, Metalgesellschaft, discloses the discharge of HDRI made from greenballs in a coal-based rotary hearth furnace (i.e. a kiln) for hot briquetting or melting. U.S. Pat. No. 6,409,790, Calderon et al., discloses the production of DRI with solid carbon and hot transfer to an oxy-melter, and the discharge of HDRI to a hot briquetting plant or insulated containers. All of these references, however, are coal-based and disclose the discharge of HDRI to one use at a time. None of the references disclose the discharge of HDRI to simultaneous multiple uses.
The concept of producing HDRI in a gas-based shaft furnace-type DR plant is also well known to those of ordinary skill in the art. For example, U.S. Pat. No. 6,162,050, Bueno et al., discloses the simultaneous discharge of HDRI to a hot briquetting plant, a melter, and a cooler. Each discharge rate is independently controlled. U.S. Pat. No. 5,296,015, Novoa et al., discloses the pneumatic transfer of hot or cold DRI from the discharge of a reduction reactor (i.e. a DR shaft furnace) to one or more points of processing, such as a hot briquetting plant, a storage bin, and/or a melter. U.S. Pat. No. 6,214,086, Montague et al., discloses the simultaneous supply of hot or cold DRI by gravity from a DR shaft furnace. The HDRI is discharged for briquetting, transporting, and/or melting. In all of these references, however, the HDRI is in the form of a pellet, lump, or agglomerate.
Thus, what is still needed in the art is a method and system for the supply of a continuous stream of HDRI from a DR shaft furnace or DRI reheating furnace to a point outside of the DR shaft furnace or DRI reheating furnace where the HDRI stream is split into at least two HDRI streams. Preferably, the first HDRI stream is sent continuously to a hot briquetting plant by gravity in a closed duct system. Preferably, the second HDRI stream is sent continuously to a melting furnace also by gravity in a closed duct system, with a surge bin and feeders, or by a combination of gravity in a closed duct system, also with a surge bin and feeders, and a generally horizontal conveyor. Optionally, a third HDRI stream is employed to continuously feed multiple hot transport vessels.